Tub for article washing machine



1963 T. E. JENKINS 3,115,885

TUB FOR ARTICLE WASHING MACHINE Filed June 25, 1962 v 2 Sheets-Sheet 1 INVENTOR. THOMAS E. :rsmqus H15 ATTO RMELY Dec. 31, 1963 T. E. JENKINS TUB FOR ARTICLE WASHING MACHINE 2 Sheets-Sheet 2 Filed June 25, 1962 F'IG.2

H \S ATTORNEY United States Patent 3,115,885 TUB FOR ARTICLE WASHING MAQIHINE Thomas E. Jenkins, Louisville, Ky., assignor to General Electr c Company, a corporation of New York Filed June 25, 1962, Ser. No. 204,911 4 Claims. (Cl. 134-176) This invention relates to tubs for article washing machines having liquid-circulating means, such as dishwashers, and more particularly to such tubs where they are formed of sheet metal and are provided with special means for preventing them from resonating at the frequency of the liquid-circulating means.

It is an object of my invention to provide, in the tub of an article washing machine, suitable structure which will provide the certainty that the resonant frequency of the tub is substantially different from the frequency of the operating means connected thereto, while at the same time insuring that the tub retains its liquid-tight nature. In one aspect of my invention, 1 provide an article washmg machine, such as a dishwasher, which has the usual tub formed of sheet metal, with means secured to and extending into the tub to cause circulation of liquid. The tub has at least one slit formed in its bottom, and a protective layer of flexible material is provided to coat the inside of the tub and, in addition, fill the slit. This provides a continuous liquid-proof coating over the entire surface of the tub regardless of the presence of the slit.

The slit is effective to change the resonant frequency of the tub bottom; this is a highly desirable attribute where, as is often the case, the tub bottom is resonant at a frequency close to one of the frequencies of the operating means. If the frequency of the tub bottom remains unmodified and is allowed to remain close to an operating frequency, then there is an amplification of the noise from the operating means which is quite disagreeable to persons in the vicinity of the machine. However, by providing the slit the resonant frequency is changed in accordance with well known principles, and the undesired amplification of noise is prevented.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. My invention, however, toge-ther with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.

In the drawings,

FIGURE 1 is a side elevational View, with some of the parts broken away to illustrate details, of a dishwasher embodying my invention;

FIGURE -2 is a cross sectional view along line 2-2 in FIGURE 1; and

FIGURE 3 is a cross section view along line 3-3 in FIGURE 2.

Referring now to FIGURE 1, there is shown an article washing machine, in this case more specifically a portable type automatic dishwasher i. The dishwasher has a dishwashing compartment 2 formed by a tub 3 with a top opening 4 adapted to be closed by a cover 5 hingedly mounted by an assembly 6 at the rear of the machine. While it may assume various configurations, tub 3 is generally of substantially rectangular configuration, as best shown in FIGURE 2, and has vertical walls I, 8, 9 and It all conventionally formed of relatively thin sheet steel which may readily be provided with the desired shape. The bottom 11 of the tub is formed as shown in FIGURE 1, having an outer slightly sloped portion 112 and an inner substantially sloped portion 13 forming a sump at the center of bottom 11.

The vertical walls 7, 8, 9 and may be continued down below the level of compartment bottom 11 so as to form ice an enclosure for an operating mechanism generally indicated by the numeral 1'4. Also, the walls may support casters 15 in any conventional manner so as to make the machine 1 movable as is well known in connection with portable dishwashers.

Within the compartment 2 there may be provided a number of dish supporting members such as an upper rack 16 and a lower rack 17 which are designed so as to support dishes and other eating and cooking articles. Dishwasher 1 incorporates suitable washing means which in this case is embodied in a rotatable water ejecting member 18 positioned below lower rack 17, together with a telescoping member 19 positioned at the center of member 18. When under pressure, member 19 rises somewhat and is provided with apertures in its top so as to eject water with substantial force against dishes in the upper rack 16 at the same time that member 18 is ejecting Water against the dishes in both racks. Arm 18 and telescoping member 19 form a part of assembly 14 which further includes a motor Zil. Motor 20 may, for instance, be of the type which, when rotated in one direction, causes a pumping assembly Z1WhiCl1 receives its water through an inlet 22 at the very bottom of sump 13to force liquid up through members 18 and 19, and which when reversed causes the pumping assembly to pass the liquid out through a conduit 23 to a drain (not shown).

It will be understood that with such a structure a complete dishwashing operation may readily be provided by means of a conventional sequence control assembly (not shown) which controls, in suitable sequence and for an appropriate number of cycles, the entry of water and washing materials, the spraying of the dishes, and the removal of the water. In addition, for drying the dishes after they have been cleansed, a suitable electric heating element 24 may be provided in the conventional manner. Element 2-4 is also under the control of the sequence control assembly so as to be energized at the end of the washing operation, and during the washing operation, if so desired, to assist in heating water.

It will be understood that all the components described thus far are conventional, and are provided in dishwashers widely available for purchase by the public.

The assembly 14 is mounted in an opening 25 formed at the center of compartment bottom 11, and is rigidly secured to the compartment bottom. This may be effected by providing a flange 26 about the assembly 14 just below pump inlet 22. A clamping ring 27 securely clamps an outwardly turned flange 28 of compartment bottom 11 to the flange 26 of the assembly 14 so that the assembly 14 is rigidly mounted, as shown, so as to extend up through the center of the compartment bottom.

While this type of structure provides a highly effective type of washing action, it has been found in the past that, although the exact relationships are not fully understood, the noise which is made by assembly 14 when it is operating may be amplified by compartment bottom 11 if the resonant frequency of the stationary parts is such as to be at all close to any frequency present in the operating means during its operation. When this sound amplification occurs, the relatively low sound level which ordinarily exists in assemblies such as that shown at 14 is amplified so as to become objectiona'bly loud and quite disagreeably noticeable to an operator in the vicinity of the machine.

As an important part of my invention, when an undesired IiOtiSE: amplification is found to be provided by compartment bottom 11, I provide a number of slits in the compartment bottom thereby changing the natural or resonant frequency of the parts, as is well known to those familiar with vibrational principles. As shown in FIGURE 2, an appropriate number of these slits may be provided, and four such slits 29, 30, 31 and 32: are actually provided in the disclosed machine.

As may be seen in connection with slit 32 by reference to FIGURE 3, the slits are preferably formed by a punching operation from the side of the tub wall which is within the tub 2 so that, in effect, a recess 33 is associated with each of the slits.

While the outer metal surface of the tub is merely exposed to the atmosphere and is therefore not subject to corrosion, the inner surfaces thereof must be protected against the corrosive effect of detergents, food acids, hot Water, etc. Accordingly, it is conventional to coat the entire inner surface of the dishwasher tub 3 with a suitable plastic material 34 so as to protect the sheet metal from these various destructive influences. Several suitable plastic materials are known to be effective for the purpose, but generally use is made of a plastic, i.e., flexible material such as either a vinyl plastic or rubber. These coatings may be applied in various ways such as, for instance, spraying the material on in liquid form and then letting it harden.

As an import-ant feature of my invention, this coating of plastic material serves not only to protect the metal of which tub 3 is formed but also serves as a plug for the slits formed in the compartment bottom, entirely plugging the slits with flexible, or plastic, material so that the continuous protective surface of the protective plastic layer is unimpaired by the presence of the slits. In fact, where, as shown, there is a recess 33 formed at each slit, the plugging eiiect of the plastic is enhanced since it will tend to fill up the recess with a pocket of plastic, as shown by the numeral 35, thereby providing a greater bonding area than where the slit is formed in an entirely flat surface.

In this manner, an effective water tight bottom is provided for the compartment 3 despite the provision of the slits 29, 30, 31 and 32 in the bottom of the tub to avoid undesirable natural frequencies.

While I have shown and described one particular embodiment of my invention I do not desire the invention to be limited to the precise construction disclosed and I intend by the appended claims to cover all such modifications which fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is;

1. An article washing machine including a tub formed of sheet metal, means secured to and extending into said tub, said means being operative to circulate liquid in said tub for Washing purposes, said tub having at least one slit formed in the bottom thereof to cause the resonant frequency of said tub to be substantially different from all frequencies of 'said means during operation thereof so as to prevent amplification by said tub of the noise of said means, and a protective coating of plastic material adhering to and coating the inside of said tub and filling said slit to provide a continuous liquid proof coating over the inside surface of said tub.

2. An article Washing machine including a tub formed of sheet metal and having an opening centrally located in the bottom thereof, means secured in said opening and extending up into said tub, said means being operative to circulate liquid in said tub for Washing purposes, said tub having at least one slit formed in said bottom to cause its resonant frequency to be substantially different from all frequencies of said means during operation thereof so as to prevent amplification by said tub of the noises of said means, and a protective coating of plastic material adhering to and coating the inside of said tub and filling said slit to provide a continuous liquid proof coating over the entire surface of said tub.

3. The structure defined in claim 1 wherein said plastic material is of the class consisting of rubber and vinyl plastics.

4. The apparatus defined in claim 1 wherein said tub is formed with a recess about said slit so as to induce filling of said recess and of said slit when said protective coating is applied in liquid form to the inside of said tub.

References Cited in the file of this patent UNITED STATES PATENTS 2,209,403 Kittner et al July 30, 1940 2,233,577 Blu Mar. 4, 1941 2,616,820 Bourgeaux Nov. 4, 1952 2,629,544 Ohmart Feb. 24, 1953 2,764,136 Gadd Sept. 25, 1956 2,808,842 Pollock et a1. Oct. 8, 1957 FOREIGN PATENTS 203,934 Austria June 10, 1959 

1. AN ARTICLE WASHING MACHINE INCLUDING A TUB FORMED OF SHEET METAL, MEANS SECURED TO AND EXTENDING INTO SAID TUB, SAID MEANS BEING OPERATIVE TO CIRCULATE LIQUID IN SAID TUB FOR WASHING PURPOSES, SAID TUB HAVING AT LEAST ONE SLIT FORMED IN THE BOTTOM THEREOF TO CAUSE THE RESONANT FREQUENCY OF SAID TUB TO BE SUBSTANTIALLY DIFFERENT FROM ALL FREQUENCIES OF SAID MEANS DURING OPERATION THEREOF SO AS TO PREVENT AMPLIFICATION BY SAID TUB OF THE NOISE OF SAID MEANS, AND A PROTECTIVE COATING OF PLASTIC MATERIAL ADHERING TO AND COATING THE INSIDE OF SAID TUB AND FILLING 